With the widespread introduction of antiretroviral therapy, HIV has become a chronic disease, and HIV- related kidney disease has emerged as an important cause of morbidity and mortality. Both HIV infection and antiretroviral therapy have been associated with kidney disease. Studies suggest that the risk of HIV-related kidney disease is increased in patients with HIV-Hepatitis C virus co-infection, but studies have not focused on the epidemiology of kidney disease in these patients. Worldwide, an estimated 40 million people are infected with HIV, and 4-5 million people are co-infected with HIV and Hepatitis C. The highest prevalence of HIV-Hepatitis C co-infection occurs in minority populations at increased risk for kidney disease. This proposal aims to investigate the epidemiology of kidney disease in patients with HIV-Hepatitis C co-infection, and to identify host and viral factors associated with increased risk. The identification of risk factors will identify patients who may benefit from enhanced screening for early detection and treatment of kidney disease. The primary objective of this application is to support the candidate's development as an independent clinical and translational investigator in the field of HIV-related kidney disease. The specific aims of this proposal are: (1) To compare the epidemiology of kidney disease in patients with HIV-Hepatitis C co-infection to that in patients with either HIV or Hepatitis C virus alone. (2) To identify host factors associated with kidney disease in patients with HIV-Hepatitis C co-infection. (3) To identify viral factors associated with kidney disease in patients with HIV-Hepatitis C co-infection. Relevance: HIV affects more than 40 million people worldwide, and kidney disease is an important complication in patients being treated for HIV. Minority patients with both HIV and Hepatitis C virus infection may be at particularly high risk for kidney disease. This study will help to identify HIV-infected patients who may be at risk for kidney disease, in order to diagnose and treat kidney disease before the development of kidney failure and other serious complications.